This invention relates to a flexible and disposable plastic bag for containing and administering medical fluids. More particularly, the invention relates to a plastic container for intravenous fluid which is blow molded in a manner such that when the contents of the bag are administered the bag will collapse in a uniform manner with opposing pleats in the side wall portions to thereby provide for accurate dispensing and determination of the bag contents.
The problems confronting the dispensing of medical fluids from flexible plastic bags are alluded to in U.S. Pat. No. 3,915,212. As indicated therein, because of the flexible nature of the bag, the bag can become distorted during emptying making it difficult to read the meniscus which is necessary to determine the amount of fluid being administered. Also as indicated in U.S. Pat. No. 4,049,033, incomplete collapse of the container can be due to the stiffness of the thin walled container which effects a resistance to collapse and a consequent moderate vacuum exerted to the container. To remedy these problems, a container is proposed in U.S. Pat. No. 3,915,212 utilizing a bag which is sealed at its edges and has a hanger portion at one end which hanger portion is reinforced to prevent uneven collapse. In U.S. Pat. No. 4,049,033, added elements are utilized in conjunction with a blow mold bag such as external shoulder portions, opposing flat end sections and gussets so as to effect a uniform collapse of a solution container.
Other versions of a blow molded, collapsible solution container are described in U.S. Pat. Nos. 4,010,783; 4,088,166; 4,090,541; 4,096,897; 4,100,953 and 4,105,730. All of the previously mentioned patents provide for the molding into the body section of the bag such features are gussets, rigid neck and shoulder portions, transverse lines of weakness, recesses and rods in the tail or hanger section of the bags to provide for gradual container collapse as the contents are dispensed.
The prior art is concerned with the molding of additional elements or features to a flexible bag in order to effect controlled collapsing. This adds to the cost of the bag and in many instances does not provide for controlled and uniform collapse of the bag walls.
It is an advantage of the present invention to provide a flexible bag for medical fluids wherein the bag walls will collapse in a manner during administration of the fluid so that accurate administration can be determined. Other advantages are a plastic solution container which can be blow molded so as to produce a bag at a minimum cost; a solution container which by controlling the wall thicknesses in a predetermined manner will result in a solution container wherein the walls will uniformly collapse during emptying; and a solution container which does not require additional elements or stiffening members to be provided in the bag structure so as to afford accurate determination of the bag contents.